JP2010125686A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device capable of reducing the occurrence of faulty ejection of ink, and suppressing an increase in the scale of the device. <P>SOLUTION: The inkjet recording device includes: an inkjet head 3 jetting aqueous ink from nozzles 13 so as to perform recording on a recording medium; a head cap 4 covering the nozzles 13 of the inkjet head 3; an intermediate tank 5 configured to communicate with the head cap 4 and store the aqueous ink ejected in the head cap 4 from the inkjet head 3 by a predetermined amount or more; and a waste liquid tank 7 configured to communicate with the intermediate tank 5 and store the aqueous ink discharged from the intermediate tank 5. The intermediate tank 5 has a ventilation path 15 through which space inside the intermediate tank 5 communicates with the outside. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inkjet recording apparatus that performs recording on a recording medium by ejecting ink from nozzles of an inkjet head.

  In an ink jet recording apparatus that prints on printing paper or the like by ejecting ink from the nozzles of an ink jet head, when water-based ink containing a certain amount of water is used as a solvent, the viscosity of the ink increases due to evaporation of water in the ink. As a result, solidification of the nozzle occurred and the nozzles were clogged.

  Therefore, a technology is known in which a head cap is attached to an inkjet head during non-printing, ink is accumulated in the head cap by flushing, and the evaporation of the ink in the nozzle opening of the inkjet head is suppressed by the vapor (for example, patent Reference 1).

There is also known a technique in which a head cap and a waste liquid tank are communicated and the nozzle openings of the ink jet head are moisturized by vapor generated from ink in the waste liquid tank (for example, see Patent Document 2).
JP 2001-261112 A JP 2007-175969 A

  However, in the technique described in Patent Document 1, since the inside of the head cap is sealed, the expansion and contraction of the air in the head cap occurs due to the mounting operation of the head cap and the change in the outside air environment during the mounting of the head cap. The ink inside was pressed to break the meniscus, resulting in ejection failure. In addition, since the line-type inkjet head has a long head configuration, the amount of ink that is ejected by flushing is not sufficient to keep the nozzle opening moist.

  Further, in the technique described in Patent Document 2, since the evaporation of ink in the waste liquid tank is suppressed, the waste liquid tank needs to have a certain amount of capacity, leading to an increase in the size of the apparatus. Further, since the ink in which the water has completely evaporated becomes easy to absorb the water, the dried ink in the waste liquid tank may absorb the water in the nozzle opening and cause the nozzle to be clogged.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet recording apparatus capable of reducing the occurrence of ink ejection failure and suppressing the enlargement of the apparatus.

  In order to achieve the above object, an inkjet recording apparatus of the present invention includes an inkjet head that performs recording on a recording medium by ejecting aqueous ink from a nozzle, a head cap that covers the nozzle of the inkjet head, and a communication with the head cap. An intermediate tank that stores a predetermined amount or more of water-based ink discharged from the inkjet head into the head cap, and a waste liquid tank that is connected to the intermediate tank and stores the water-based ink discharged from the intermediate tank. The intermediate tank has an air passage that communicates the space inside the intermediate tank with the outside.

  In the ink jet recording apparatus of the present invention, the air passage is composed of a long tubular member that forms a humidity gradient in which the humidity decreases from the inner side to the outer side of the intermediate tank.

  In the ink jet recording apparatus of the present invention, the leading end of the air passage is led to a space in the waste liquid tank.

  The waste liquid tank in the inkjet recording apparatus of the present invention is always open to the atmosphere.

  Further, the water-based ink in the ink jet recording apparatus of the invention includes a humectant.

According to the ink jet recording apparatus of the present invention, it is possible to reduce the occurrence of ink ejection failure and to suppress the enlargement of the apparatus.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals, and the description thereof is omitted or simplified.

  FIG. 1 is a schematic configuration diagram showing an ink jet recording apparatus according to an embodiment of the present invention. As shown in FIG. 1, the ink jet recording apparatus according to this embodiment includes an ink tank 1, a pump 2, an ink jet head 3, a head cap 4, an intermediate tank 5, a pump 6, and a waste liquid tank 7. , Pump drive units 8 and 9, head drive unit 10, cap moving mechanism 11, and control unit 12. The ink jet recording apparatus according to the present embodiment is an apparatus that performs recording using water-based ink that is ink containing a certain amount of water in a solvent.

  The ink tank 1 holds aqueous ink, and the pump 2 supplies the ink in the ink tank 1 to the inkjet head 3.

  The inkjet head 3 includes a plurality of nozzles 13 and ejects ink supplied from the ink tank 1 from the nozzles 13 to perform recording on a recording medium (not shown) such as printing paper.

  The head cap 4 is formed of a soft material such as rubber, and functions as a lid that covers the nozzle 13 by adsorbing to the inkjet head 3 during a recording operation pause period and prevents the opening of the nozzle 13 from drying. It functions as an ink receiver during the pressure purge operation.

  Although illustration is omitted, a plurality of inkjet heads 3 are provided corresponding to each color, and a plurality of ink tanks 1, pumps 2, and head caps 4 are also provided correspondingly.

  The intermediate tank 5 communicates with each head cap 4 via a path 14 so that the ink ejected from the inkjet head 3 into the head cap 4 is guided, and stores a predetermined amount or more of this ink. Steam generated from the ink stored in the intermediate tank 5 is supplied into the head cap 4 through the path 14 to keep the opening of the nozzle 13 moisturized. The passage 14 connecting the head cap 4 and the intermediate tank 5 is preferably formed by a thin and short rubber tube having an inner diameter of 2.5 mm and a length of about 5 cm, for example, in order to facilitate supply of steam into the head cap 4.

  The upper wall 5a of the intermediate tank 5 is provided with a ventilation path 15 for communicating the space inside the intermediate tank 5 with the outside to release the atmosphere. The ventilation path 15 is formed in a labyrinth structure by a long tubular member. A humidity gradient in which the humidity decreases from the inner side to the outer side of the intermediate tank 5 is formed inside the air passage 15, and the release of vapor generated from the ink in the intermediate tank 5 is suppressed. It has become so. The air passage 15 is formed of, for example, an elongated rubber tube having an inner diameter of 2.5 mm and a length of about 50 cm.

  The intermediate tank 5 includes a first liquid level detection sensor 16 that detects a liquid level that is the upper limit of the stored ink amount, and a second liquid that detects the liquid level that is the lower limit of the stored ink amount. A surface detection sensor 17 is provided. Detection signals from the first and second liquid level detection sensors 16 and 17 are output to the control unit 12.

  The pump 6 supplies the ink in the intermediate tank 5 to the waste liquid tank 7. The waste liquid tank 7 stores the ink discharged from the intermediate tank 5 by the pump 6. The waste liquid tank 7 is always open to the atmosphere so that the water content of the ink in the waste liquid tank 7 is easily evaporated.

  Pump drive units 8 and 9 drive pumps 2 and 6, respectively. The head drive unit 10 drives the ink discharge operation of the inkjet head 3. The cap moving mechanism 11 moves the head cap 4 to attract the head cap 4 to the inkjet head 3 during the pause period of the recording operation. The control unit 12 controls the pump driving units 8 and 9, the head driving unit 10, and the cap moving mechanism 11.

  Next, the operation of the ink jet recording apparatus according to this embodiment will be described.

  When a pause period during which recording on the recording medium is not performed, the control unit 12 controls the cap moving mechanism 11 so that the head cap 4 is moved and attracted to the inkjet head 3.

  Here, although the intermediate tank 5 communicating with the head cap 4 is opened to the atmosphere by the air passage 15, the air passage 15 has an elongated labyrinth structure, and therefore, when the head cap 4 is attracted to the inkjet head 3, A slight pressure may be generated in 4.

  At this time, if pressure exceeding the strength of the meniscus formed on the nozzle 13 is applied to the nozzle 13, bubbles may enter the nozzle 13, leading to ink ejection failure or clogging of the nozzle 13. For this reason, when the head cap 4 is attracted to the inkjet head 3, it is preferable to press the head cap 4 against the inkjet head 3 at a low speed so that pressure exceeding the strength of the meniscus is not applied to the nozzle 13. .

  When the head cap 4 is adsorbed to the ink jet head 3, the control unit 12 drives the pump 2 to pump ink to the ink jet head 3 to discharge the ink from the nozzle 13 so as to perform a so-called pressure purge. The pump drive unit 8 is controlled.

  The ink ejected from the nozzles 13 by this pressure purge operation is received by the head cap 4 and then introduced into the intermediate tank 5 via the path 14.

  Here, when the first liquid level detection sensor 16 detects the ink level, the controller 12 drives the pump 6 to discharge a predetermined amount of ink from the intermediate tank 5 to the waste liquid tank 7. The pump drive unit 9 is controlled.

  As described above, ink is stored in the intermediate tank 5. During the mounting of the head cap 4 on the inkjet head 3, vapor generated from the ink in the intermediate tank 5 is supplied into the head cap 4 via the path 14, and the opening of the nozzle 13 is moisturized. Occurrence of clogging of the nozzle 13 due to an increase in ink viscosity or solidification of ink is suppressed.

  Since the intermediate tank 5 is opened to the atmosphere by the air passage 15, the expansion and contraction of the air in the head cap 4 communicating with the intermediate tank 5 does not occur even when the outside air environment changes, and the meniscus negative of the nozzle 13 is negative. The pressure state can be maintained.

  On the other hand, since the air passage 15 has an elongated labyrinth structure, it is possible to suppress the vapor generated from the ink in the intermediate tank 5 from being released to the outside. For this reason, the humidity in the head cap 4 can be kept substantially constant and a good moisturizing state can be maintained.

  It is necessary to evaporate the water in the ink, but it has been experimentally confirmed that the nozzle 13 is clogged due to the supersaturation of the water in the head cap 4. Therefore, in the present invention, for example, it is preferable to use a water-based ink containing a water-soluble solvent having an OH group having a water content of 50% or less and a boiling point of 250 ° C. or more as a humectant. Thereby, the clogging of the nozzle 13 due to the supersaturation of the water in the head cap 4 described above can be prevented.

  As described above, in the present embodiment, the air passage 15 has an elongated labyrinth structure to suppress the evaporation of ink in the intermediate tank 5. However, as long as the intermediate tank 5 is open to the atmosphere, the middle The ink in the tank 5 is slightly reduced by evaporation. When the ink in the intermediate tank 5 decreases and the second liquid level detection sensor 17 detects the ink level, the control unit 12 drives the pump 6 to transfer the old ink in the intermediate tank 5 to the waste liquid tank 7. The pump drive unit 9 is controlled so as to be discharged.

  After the old ink is discharged from the intermediate tank 5, the control unit 12 controls the pump drive unit 8 to execute the pressure purge, and supplies fresh ink into the intermediate tank 5. By this pressure purge, an amount of ink that forms a liquid level above the detection position of the second liquid level detection sensor 17 is accumulated in the intermediate tank 5.

  In this way, by storing a predetermined amount or more of fresh ink in the intermediate tank 5 at all times, even when the inkjet head 3 has a line-type long head configuration, a good moisturizing state in the head cap 4 is maintained. .

  As described above, according to the present embodiment, the intermediate tank 5 is provided between the head cap 4 and the waste liquid tank 7, and the intermediate tank 5 is separated from the ink in the intermediate tank 5 by the labyrinth-structured air passage 15. Since the generated steam is released to the atmosphere while preventing the generated steam from being released to the outside, the nozzle 13 is moisturized by the steam generated from the ink stored in the intermediate tank 5 and the air in the head cap 4 is expanded. It is possible to suppress the destruction of the meniscus of the nozzle 13 due to the shrinkage, and to reduce the occurrence of ink ejection failure at the nozzle 13.

In addition, the waste liquid tank 7 is always open to the atmosphere, and the water content of the ink in the waste liquid tank 7 is always evaporated, so that a large amount of waste ink can be received without increasing the size of the waste liquid tank 7, thereby increasing the size of the apparatus. Can be suppressed.
As shown in FIG. 2, the air passage 15 may have its tip guided to a space 18 in the waste liquid tank 7. The space 18 has a higher humidity than the outside air due to the vapor generated from the ink in the waste liquid tank 7. For this reason, by arrange | positioning the front-end | tip of the ventilation path 15 in the space 18, it can suppress more that the vapor | steam in the intermediate tank 5 is discharge | released outside.

  Further, the labyrinth-structured air passage 15 may be omitted, and a small hole for ventilation may be provided in the upper wall 5a of the intermediate tank 5. Thereby, although the evaporation suppression effect in the intermediate tank 5 is slightly reduced, the apparatus configuration can be simplified.

  Further, the intermediate tank 5 may not be used in common for the plurality of inkjet heads 3, but may be provided for each inkjet head 3.

  As mentioned above, although embodiment in this invention was described in detail, this invention can be implemented in other various forms, without deviating from the summary. The foregoing embodiments are merely illustrative in all respects and should not be construed as limiting. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

1 is a schematic configuration diagram illustrating an ink jet recording apparatus according to an embodiment of the present invention. It is a figure which shows the ventilation path by which the front-end | tip was guide | induced to the space in a waste liquid tank.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ink tank 2,6 Pump 3 Inkjet head 4 Head cap 5 Intermediate tank 7 Waste liquid tank 8, 9 Pump drive part 10 Head drive part 11 Cap moving mechanism 12 Control part 13 Nozzle 15 Ventilation path

Claims (5)

An inkjet head that records water on a recording medium by ejecting water-based ink from a nozzle;
A head cap that covers the nozzle of the inkjet head;
An intermediate tank connected to the head cap and storing a predetermined amount or more of water-based ink discharged from the inkjet head into the head cap;
A waste liquid tank that communicates with the intermediate tank and stores aqueous ink discharged from the intermediate tank;
2. The ink jet recording apparatus according to claim 1, wherein the intermediate tank has an air passage that communicates the space inside the intermediate tank with the outside.   2. The ink jet recording apparatus according to claim 1, wherein the air passage is composed of a long tubular member that forms a humidity gradient in which the humidity decreases from the inner side to the outer side of the intermediate tank.   The inkjet recording apparatus according to claim 2, wherein a leading end of the air passage is led to a space in the waste liquid tank.   The inkjet recording apparatus according to claim 1, wherein the waste liquid tank is always open to the atmosphere. The inkjet recording apparatus according to claim 1, wherein the water-based ink includes a humectant.

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